The present invention relates to tube-connection systems, and particularly to a process of connecting a spindle or the like to a tube. More particularly, the present invention relates to a press-fit tube-connection system.
Many conventional pieces of furniture are constructed of metal tubes that are joined together to yield a sturdy unit. For example, it is known to produce juvenile products such as cribs, cradles, toddler beds, high chairs, and dressing tables by welding steel tubes together to form the various side panels, end panels, frames, legs, etc. included in those products. Of course, many types of furniture other than juvenile products include welded metal tubular components.
What is needed is an improved process for manufacturing sturdy pieces of furniture which include tubular components so that it is not necessary to weld such tubular components to one another to anchor tubular components to one another during assembly. Such a process would be welcomed by manufacturers of juvenile furniture desirous of minimizing manufacturing costs and enhancing furniture quality and appearance.
According to the present invention, a method is provided of connecting a spindle to a tube. The method includes the steps of punching a non-round hole in an exterior wall of the tube and press-fitting an end portion of the spindle into the non-round hole to establish a tight fit between the spindle and the tube. The fit is tight enough so as to retain the spindle in coupled relation to the tube.
In preferred embodiments of the present invention, the punching step is completed using a scissors punch including a shank for mounting in a punch press and two sharpened downwardly projecting tube-piercing tips. The tube is placed in a support fixture and the scissors punch is moved to engage the tube so that the tube-piercing tips puncture an exterior wall of the tube and other edges on the downwardly projecting end of the scissors punch slice through other portions of the exterior wall to form the non-round hole therein. Next, the scissors punch is withdrawn from engagement with the tube and a spindle is inserted into the non-round hole and moved therein to establish a tight fit between the spindle and the punctured tube. By sizing the punch to produce a properly sized hole for a given spindle, it is thus possible to connect a spindle to a tube using the method of the present invention without welding the spindle to the tube.
The spindle-receiving hole formed in the tube using a method in accordance with the present invention is not round and the term "non-round" is used herein to characterize a hole that is not circular or round. Illustratively, a suitable non-round hole could appear to have a somewhat oblong shape. The perimeter border of a suitable non-round hole formed in accordance with the method of the present invention could also be defined by an irregularly shaped or undulating edge in the tube that is created during the punching step. Illustratively, the outer diameter of the spindle is greater than the nominal inner diameter of the non-round spindle-receiving hole formed in the tube.
Illustratively, the spindle, once press-fit into a non-round hole formed in a tube, does not "bottom out" on an inner wall of the tube opposite to the spindle-receiving non-round hole, but rather the spindle extends a distance into the hollow tube that is about one-half of the inner diameter of the tube so as to prevent removal of the press-fit spindle from the non-round hole formed in the tube. Frictional engagement of the spindle and the tube prevents the spindle from backing out of the non-round hole formed in the tube. Advantageously, it is not necessary to weld the spindle to the tube at the junction therebetween to couple the spindle securely to the tube once the two elements have been coupled together using the method of the present invention.
It is within the scope of the present invention to press-fit various members into holes formed in tubes. Within this application, "spindle" is used to refer to various spindles, rods, tubes, or other generally elongated members of the type used in the construction of furniture.
Ideally, the method of the present invention is used to couple metal tubular spindles to metal tubes to produce subassemblies used in the construction of furniture for use by juveniles. Illustratively, such a method could be used to produce side panels and end panels of cribs, cradles, and beds. In addition, the method could be used to manufacture portions of high chairs, swings, dressing and changing tables, and other juvenile products. Of course, it will be understood that the method is not limited for use only in connection with the manufacture of juvenile products, but could be used to make a wide range of furniture items constructed using tubular elements.
It is within the scope of the invention to punch many holes in one tube simultaneously and then press-fit one spindle into each of the holes punched in the tube so that a series of spindles are aligned in perpendicular relation to the tube and coupled in fixed relation to the tube. Such a method is well-suited for use in manufacturing side panels or end panels in metal tubular cribs, cradles, and the like.
Additional objects, features, and advantages will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.